Rather than simply posting a Google search that he can do himself, let me recommend an actual title that I've found useful here in Virginia: "Native Trees of the Southeast," by Kirkman et al. It includes range maps, summer and winter keys, and good color photos, including bark for many species. Not overly technical, but a good overview.
Mr. Roller hasn't specified what sort of fieldwork he's doing, so it's difficult to know exactly what he's looking for; but if winter condition will be a factor, then I would also suggest Ron Lance's "Woody Plants of the Southeastern United States: A Winter Guide," which emphasizes detailed keys, and also covers the more common invasives and escaped cultivars as well as native species. - John A.
